Apparatus responsive to temperature conditions



April 2, 1957 L. H. WASHBURN 2,787,685

APPARATUS RESPONSIVE To TEMPERATURE CONDITIONS Filed July 27, 1954 QAWUnited States Patent APPARATUS RESPONSIVE T0 TEMPERATURE CONDITIONSLucius Henry Washburn, Alfred, N. Y.

Application July 27, 1954, Serial No. 446,078

9 Claims. (Cl. 200-142) This invention relates to apparatus which isresponsive to temperature conditions. It is particularly concerned withapparatus adapted to be used with a kiln or furnace to indicate thetemperature conditions therein or to modify such conditions.

It is an object of the invention to provide an inexpensive apparatus forindicating the temperature conditions within a kiln or furnace.

Another object of the invention is to provide apparatus of the characterdescribed which is simple and of inexpensive construction.

A further object of the invention is to provide apparatus of thecharacter described which is adapted for use in furnaces or kilns ofdifferent types.

Another object of the present invention is to provide apparatus of thecharacter described which may be adapted either for calling attention totemperature conditions within a kiln or furnace or for modifying suchtemperature conditions.

Another object of the invention is to provide apparatus of the characterdescribed which is dependable in operation and utilizes readilyobtainable and inexpensive replaceable elements.

Other objects and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings in which:

Figure 1 is a perspective view of a kiln embodying apparatus accordingto the present invention;

Figure 2 is an enlarged perspective view of a modified form of cradle orcage for the replaceable heat-responsive elements; and

Figure 3 is a transverse sectional view taken on the line 33 of Figure2.

In the manufacture of ceramic products the firing of the products is oneof the most expensive and diflicult steps. Proper firing is not merely amatter of raising the temperature of a kiln in which the products havebeen placed. Rather, it is necessary to maintain definitetimetemperature relationships throughout the firing period and also totake into account the chemical composition of the ceramic bodies in thekiln and the shapes, thicknesses and masses of those bodies. Thematuring temperature of a ceramic body, i. e. the temperature at whichthe body has the desired density and degree of vitrification, varieswith the rate of heating. Consequently, a device which measures only thekiln temperature will not necessarily show whether the ware in the kilnhas been properly matured. If the proper temperature is not reached theware in the kiln will be weak and porous. On the other hand, if thematuring temperature is exceeded the ware may be excessively dense andhard and may be warped.

Although temperature indicating devices such as recording pyrometers areused to a considerable extent in the firing of ceramic products, suchapparatus is expensive and is not feasible for many users of kilns. As ameans of determining whether proper firing conditions are beingmaintained in a kiln and when the maturing temperature of ceramic waretherein has been reached,

pyrometric cones have come into general use. These cones are slendertrihedral pyramids formed from mixtures of ceramic materials. Since suchcones have compositions similar to those of ceramic ware, theirreactions in kilns at elevated temperatures may be correlated to that ofthe ware in the kilns with considerable accuracy.

Pyrometric cones are obtainable which soften and progressively deform bybending under advancing heat at fairly regular temperature intervalsover a long temperature range. In use, such cones are placed onrefractory bases or supports at one or more points within a kiln Wherethey may be observed through a peephole provided in the kiln door orwall. Normally, a series of cones is used in each of the locationschosen. Each such series usually contains one or more cones which softenand bend over at a temperature below the maturing temperature of theware in the kiln, a cone which softens and bends when the maturing pointis reached, and one or more cones which soften at higher temperaturesand will not bend unless the kiln is overfired. By observation of such aseries of cones it may then be ascertained (1) when the maturing pointof the ware is approaching, (2) when firing should be discontinued, and(3) to what extent, if any, overfiring has occurred.

It will be realized that to keep watch on pyrometric cones through apeephole requires a considerable amount of attention and expenditure oftime. By the present in" vention pyrometric cones may be used toindicate temperature conditions within a kiln in such a way that it isunnecessary to continually or periodically observe the cones since thedeformation of a cone or cones will result in the sounding of an alarmor the taking of other desired and predetermined action. An embodimentof apparatus for using a pyrometric cone in this way is shown in theaccompanying drawings and described hereinafter in connection with anelectrically heated kiln.

As shown in Figure l, the kiln 11, which is formed of refractorymaterial of any suitable type, has had its front removed to better showthe heating chamber 12 therein. Arranged around the interior of theheating chamber are electrical heating elements, designated by thereference numeral 13, which may be of any desired and suitable type.Such elements are connected to a suitable source of electric power,preferably through means (not shown) by which the power supplied to thekiln may be regulated.

As made clear in Figure 1, a small hole or orifice 16 is providedthrough the top wall of the kiln 11. Extending through the hole 16 andfreely movable therein is a supporting rod 17. The rod 17 is providedwith a threaded portion 18 on the upper end thereof and has its lowerend formed as a hook 19. Supported by the hook 19 is a cage or cradle,generally designated by the reference numeral 22, within which apyrometric cone 23 is held in an upright, but inclined position. Thecage 22, which preferably is formed of heat-resistant wire such, forexample, as wire made of nickel or nickel-chromiumiron alloys likeInconel comprises a pair of generally oval, side-frame members 26 and 27that are joined and held in spaced, parallel relation by a plurality ofribs or cross bars 28, 29, 30 and 31. When the cradle 22 is suspendedfrom the hook 19 by the top rib 28, the lower ribs 29 and 30 are sodisposed with respect to the intermediate rib 31 that the pyrometriccone 23 when resting with its base on the lower ribs is supportedadjacent its tip by the intermediate rib 31.

A switch 36 is mounted on the top of the kiln 11 by suitable means, suchas mounting brackets 37, and is provided with an elongated, operatingarm or lever 38. The latter extends substantially horizontally andparallel with the top of the kilns. Adjacent its outer end the lever 38is provided with a hole through which the threaded end portion 18 of thevertical rod 17 projects,

the rod being held within said hole by a threaded nut 41. Secured to thetop 13 of the kiln 11 intermediate the switch 36 and the rod 17 is ayoke or inverted U- shaped bracket 42. The loke 42 projects upwardlyfrom the kiln and comprises vertical legs 4 and which are joined attheir upper ends by a horizontal portion 47. A hole is provided in thelatter in which there is slidably arranged a vertical stud 48 having anut 49 threaded thereon.

A coil spring 51 is attached to the lower of thestud 43 and to theadjacent portion of the switch operating arm 38. The tension of thespring may be adjusted by turning the nut 4-9 to thereby raise or lowerthe stud 48 in the horizontal portion d7 of the yoke. Attached to theswitch 36 and extending to a junction box 54 are a pair of leads 56 and57. Other desired or necessary electrical connections such as the wires53 and 59 may also be led to the junction be): 54 to permit establishingthe desired electrical circuits.

The operation of apparatus according to the present invention dependsupon the characteristic softening and deformation of pyrometric cones inresponse to the achievement of certain temperature conditions within akiln. With apparatus as shown in Figure l, the kiln is closed and firingis started. When predetermined temperature conditions have been obtainedin the kiln the pyrometric cone 23 will soften and deform sufiicientlyto drop out of the cradle or cage 22 solely by its own weight. Theweight suspended on the outer end of the arm 33 by the rod 17 willthereby be diminished and the spring 51 will move the arm 33 upwardlythereby to actuate the switch 36. It will be understood that actuationof the switch 36 may produce any one or several of a number ofpredetermined results depending upon the electrical circuits providedand the type and arrangement of the switch. Thus, for example, movementof the lever 38 to actuate the switch 36 may produce, directly or by useof suitable relays, either the giving of a signal, either visual,audible, or both, or the cutting oil or reduction of power supplied tothe kiln, or, desired, any combination of such actions.

As pointed out above, the usual practice in operation of a kiln is toemploy a series of pyrometric cones for determining the point at whichfiring should be discontinued. When using the apparatus illustrated inFigure l, the pyrometric cone 23 used may be so chosen that the propertime for shutting off the kiln 11 is indicated by the softening of thecone and its dropping out of the cradle 22. In such case the switch 36may be so connected to a suitable circuit that the power supply to thekiln is interrupted when the switch is actuated by the spring 51. Ifdesired, however, actuation of the switch 36 may cause an audible orvisible signal to be given. An attendant or operator, whose attention isattracted by such signal, may then shut off the kiln manually.Alternatively, if desired, the cone 23 may be so chosen that it softensand deforms before the maturing temperature is reached. In that casewhen the cone drops from the cage or cradle 22 the resultant operationof the switch 36 may give a suitable signal indicating that the time forshutting ofi the kiln is approaching. An operator may then observe aseries of pyrometrie cones within the kiln through the peep holeprovided and determine therefrom when firing should be discontinued.

in Figures 2 and 3 there is illustrated a modified cage or cradle 61which is adapted to hold two pyrometric cones. Like the cradle 22, thecradle 61 is formed of heat resistant wire and comprises a pair of sideframe members 66 and 67 which are maintained in spaced, parallelposition by a plurality of cross-bars or ribs 68, 69, 7Q, 71, 72, 73 and74. The last-mentioned rib is engaged by the hook 19 of the vertical rod17 to support the cage within a kiln 11. The cones 62 and 63 are placedwithin the cradle 61 so that their bases rest against the lowercross-bars 70, 71 and 72, 73, respectively, while the cones aresupported adjacent their tips by the intermediate ribs 68 and 69,respectively. Adjacent the lower portion of the cage 61 there is alsoprovided a peripheral rail 76 that prevents the cones from falling outof the cage before they are deformed by heat.

it will be evident that in some cases the use of the modified form ofcage 61 with a pair of pyrometric cones permits even more convenient andefficient operation of a kiln than is possible with the single conearrangement illustrated in Figure 1. Thus, for example, one of the conesplaced in the cage 61, such as the cone 62, may deform and consequentlydrop from the cage at a temperature somewhat below the maturingtemperature, while the other cone, 63, may be so chosen as to deform anddrop when the maturing temperature is reached. Raising of the arm orlever 33 and actuation of the .witch 36 under the influence of thespring 51 when the cone 62 drops from the cradle may cause the soundingof an alarm, as by a hell or light, indicating this fact to theattendant or operator. Thereupon, if desired, spring tension may bereadjusted by rotating the nut 49 on the stud 48 so that the switch 36may again be actuated to shut off the current to the kiln and preventoverfiring of the ware therein when the second cone, 63, deforms at thematuring temperature.

in the foregoing description it will be apparent that the apparatus ofthe present invention may be conveniently and effectively used in thefiring of ceramic products to prevent overfiring thereof and to avoidthe need for constant attention to a kiln during firing. The apparatuswhich is simple and easily assembled on or removed from a kiln utilizesto maximum advantage pyrometric cones which are commerciallymanufactured and easily available. Moreover, the only parts which willrequire frequent replacement are the pyrometric cones employed and theseare quite inexpensive. In use, in the apparatus, a cone is supportedonly at its base and adjacent its tip and has no load or pressureapplied thereto. Consequently, there is no interference with the normalfunctioning of the cone and it will deform in response to heating insubstantially the same way as it would if placed on a refractory plaque.It will be understood that while a single temperature conditionindicator according to the invention will be sufiioient for small kilns,in larger kilns a plurality of such indicators placed at differentlocations in the kiln may be desired. In such case certain of theindicators may be so arranged as to warn of uneven temperatureconditions while one or more others may be arranged to shut off the kilnwhen the maturing temperature is attained.

It will also be understood that many modifications and variations in thestructure described and in the use of the apparatus may be made withoutdeparting from the spirit of the invention. For example, the shape orconstruction of the cages 22 and 61 may be varied as desired orconvenient and the latter, if desired may be enlarged to hold more thantwo cones. Further, for example, the coil spring 51 may be replaced by atension spring of another type or by an adjustable compression springsupporting the arm or lever 38. As previously pointed out, actuation ofthe switch 36 by change of weight depending from the arm 38 may becaused to establish electrical circuits for performing any desiredfunction. Consequently, the switch may be either normally closed ornormally open, as desired, and any suitable electrical circuits may beattached or connected thereto. In this connection, it may be noted thattemperature responsive apparatus of the type herein described is notlimited to use with electrically heated furnaces but may be used toadvantage with furnaces heated in other ways. In view of the foregoing,it is desired that the invention shall not be considered as limited tothe structure of the apparatus herein described and shown but that itshall be interpreted as broadly as permitted by the terms of theappended claims.

I claim:

aromas 1. Apparatus for indicating temperature conditions within a kilncomprising a movable cradle within said kiln, means outside of said kilnresponsive to movement of said cradle, and ceramic means carried by saidcradle and adapted to fall therefrom solely by its own weight inresponse to predetermined temperature conditions within said kiln.

2. Apparatus for indicating temperature conditions within a kilncomprising a movable cradle within said kiln, means outside said kilnresiliently supporting said cradle, ceramic means carried by said cracneand adapted to fall therefrom solely by its own weight in response topredetermined temperature conditions within said kiln, and meansoperatively connected to said supporting means responsive to movement ofsaid cradle.

3. Apparatus for indicating temperature conditions within a kilncomprising a movable cradle within said kiln, means outside said kilnsupporting said cradle, ceramic means carried by said cradle and adaptedto fall there from solely by its own weight in response to predeterminedtemperature conditions within said kiln, means connected to saidsupporting means resiliently opposing the weight of said cradle, andmeans operatively connected to said supporting means responsive tochanges in weight of said cradle.

4. Apparatus as set forth in claim 3 in which said resilient means isadjustable.

5. Apparatus for indicating temperature conditions within a kilncomprising a movable cradle within said kiln, means outside said kilnresiliently supporting said cradle, and control means connected to saidsupporting means and operable thereby, said cradle being adapted to holda pyrometric cone in such manner that under pre determined temperatureconditions within said kiln said cone will deform and fall from saidcradle solely by its own weight, thereby causing movement of saidsupporting means and operation of said control means.

6. Apparatus as set forth in claim 5 in which said control means is aswitch.

7. Apparatus for indicating temperature conditions within a kilncomprising a movable cradle within said kiln, a pyrometric cone restingwithin said cradle and adapted under predetermined temperatureconditions to deform and fall from said cradle solely by its own weight,an arm outside of said kiln, said cradle being suspended from said arm,means connected to said arm and resilient- 1y opposing the weight ofsaid cradle, and control means operable by movement of said arm inresponse to change of weight of said cradle.

3. Apparatus as set forth in claim 7 in which said cone is supportedsolely at its base and adjacent the tip thereof.

9. Apparatus as set forth in claim 8 in which said control means is aswitch.

References Cited in the file of this patent UNITED STATES PATENTS

